Since 1960s, aperture patterns have been studied extensively and a variety of coded apertures have been proposed for various applications, including extended depth of field, defocus deblurring, depth from defocus, light field acquisition, etc. Researches have shown that optimal aperture patterns can be quite different due to different applications, imaging conditions, or scene contents. In addition, many coded aperture techniques require aperture patterns to be temporally changed during capturing. As a result, it is often necessary to have a programmable aperture camera whose aperture pattern can be dynamically changed as needed in order to capture more useful information. In this paper, we propose a programmable aperture camera using a Liquid Crystal on Silicon (LCoS) device. This design affords a high brightness contrast and high resolution aperture with a relatively low light loss, and enables one change the pattern at a reasonably high frame rate. We build a prototype camera and evaluate its features and drawbacks comprehensively by experiments. We also demonstrate two coded aperture applications in light field acquisition and defocus deblurring.